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What is a gene? A unit of inheritance A favorite article of clothing A small portion of a DNA molecule that codes for a protein and thus determines a trait. From Gene to Protein. 1 and 3. Proteins. These are essential macromolecules. Make up about 15% of the mass of a human.
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What is a gene? A unit of inheritance A favorite article of clothing A small portion of a DNA molecule that codes for a protein and thus determines a trait. From Gene to Protein 1 and 3
Proteins • These are essential macromolecules. • Make up about 15% of the mass of a human. • Most of the rest of the body (65-90%) is made of_______? • Builds and repairs body tissue including muscle • Make up enzymes. • Make up molecules in the immune system and hormones, which regulate bodily functions such as sex drive. WATER
Proteins are absolutely essential for good health! • Below are diagrams of the structures of different types of proteins. Their complex structures led many scientists to believe… genes were carried on proteins NOT DNA
More about Proteins • Proteins coordinate cellular activities—they allow cells to communicate with each other. They control vital functions like the beating of your…
And more… • Proteins are involved in molecular transport. • Hemoglobin is the protein in your blood that makes it RED. It carries oxygen from your lungs to all of the cells in your body. • Oxygen is used for which cellular process? • What is the purpose of this process?
And more… • Proteins are made of amino acids. • There are 20 different amino acids that can combine to make thousands of proteins found in a human. • Your body KNOWS which proteins to produce because of the DNA code! • The code is written in the letters A-T-C-G.
From Gene to Protein • Each gene on a DNA molecule provides the directions (in code) for making 1 type of protein. • The protein may determine the color of your hair, or if you think broccoli has a bitter taste.
The pattern of the bases on the DNA is a code. Each base is like a letter of an alphabet In the DNA "alphabet" there are 4 “letters” Each of the nitrogen bases is one letter: GCTA How does information on a DNA molecule get used to make proteins?
How does information on a DNA molecule get used to make proteins? • Each word in the DNA "alphabet" is 3 letters long. • Each word can be spelled out in any combination of the 4 bases. • 64 possible "words“ = 43. Each word is translated into an amino acid.
How does information on a DNA molecule get used to make proteins? • There are only 20 different amino acids produced by the DNA alphabet. • Since there are 64 possible "words", this means most amino acids can be spelled in several ways.
How does information on a DNA molecule get used to make proteins? • Long chains of amino acids make up a protein--the proteins make up our traits! • An individual gene on a DNA molecule contains all of the nitrogen bases to “spell out” one protein. • 1 gene = 1 protein • If the code is incorrect the wrong amino acids are produced create the wrong proteins MUTATIONS
All begins in the Nucleus! • The code is copied from the DNA molecule by messenger RNA (mRNA). • This process is called transcription. • It takes place in the nucleus of the cell
Messenger RNA • mRNA is similar to DNA except • It is much shorter than DNA • It is only made of one strand NOT two • It has four nitrogen bases • Cytosine matches with Guanine • Adenine matches with Uracil
Messenger RNA • This is how mRNA works. • A section of one strand of a DNA molecule has the nitrogen bases: TCGATCCCA • mRNA uses complementary bases to match the sequence. Because it is RNA the “A” (adenine) matches with “U” (uracil). AGCUAGGGU • Transcription
In the Cytoplasm! • After transcribing a small section of DNA the mRNA leaves the nucleus and enters the cytoplasm. • There it attaches itself to a ribosome containing ribosomal RNA (rRNA).
Translation • At the ribosome, the code is read by transfer RNA (tRNA) • This process is called translation. • tRNA reads the code and builds a protein from the information.
Translation • The code is read as a series of three letter “words”. • Each three-letter word is called a CODON. • Each codon specifies a different amino acid. Transcription and Translation GCA = ALANINE